Intervention Studies

Intervention studies are broadly defined as those that include an action or component intended to promote health or prevent disease by influencing, affecting, or manipulating environmental, behavioral, or etiological aspects of a disease. In other words, an intervention is designed with the express intention of improving health at the individual or group level. One of the most famous interventions in modern biomedicine occurred in 1854 when John Snow, a medical doctor, advocated removing the pump handle from a public water pump located on London's Broad Street. Snow believed that the Broad Street pump was the source of contaminated water contributing to a cholera [Page 562]epidemic in the city. Snow's earlier observations of cholera convinced him that the disease was transmitted through direct physical contact with contaminated individuals or other contaminated sources. Therefore, he believed, the simple act of removing the handle from the Broad Street public pump, which was located within the community where most of the cholera infections were clustered, would prevent further exposure to local residents.

Snow's idea was controversial among the mainstream public as well as among many of his medical colleagues, for it was commonly accepted at the time that cholera was spread by miasma (i.e., bad air). However, removing the handle from the Broad Street pump, which rendered it unusable and forced local residents to find alternative water sources, coincided with a dramatic decrease in cholera outbreaks in the London neighborhood. It was later determined that the Broad Street pump was adjacent to a sewage catchment area that had been contaminated by Vibrio cholerae bacteria, and the cholera-laden sewage had subsequently seeped into the public water supply. Although it has been suggested that the epidemic was already receding before Snow removed the handle from Broad Street's pump, the phrase ‘removing the pump handle’ remains a popular metaphor among public health practitioners more than 100 years after Snow's intervention challenged both standard medical authority and popular opinion of his day. The Broad Street pump episode came to reflect the importance of the emerging discipline of epidemiology as a tool for enhancing public health through identification of disease-causing agents and development of intervention studies able to systematically measure the efficacy of treatments to attenuate or prevent disease.